The present invention relates generally to probe adapters for measurement probes and more particularly to a probe tip adapter usable with very high frequency single ended and differential measurement probes.
Probe tip adapters are accessories developed for measurement probes to allow probing of various types of electrical components. The adapters allow connections to square pins mounted on a circuit board, ground points on the circuit board, leads of surface mounted integrated circuit devices, and the like. The P6243 Active Measurement Probe 10, manufactured and sold by Tektronix, Inc., Beaverton, Oreg. and assignee of the instant invention, has a socket type probe tip 12 and ground socket 14 as shown in FIG. 1 and depicted in design patent DES U.S. Pat. No. 354,923. The socket tip has an overall length of 0.255 inches and a diameter of 0.065 inches. The socket bore has a diameter of 0.038 inches and a length of 0.225 inches. Various types of probe tip adapters are inserted into the socket to allow various types of probing.
A positioning aid probe tip adapter 16, described in U.S. Pat. No. 5,387,872, has a housing 18 with a central bore 20 there through that receives a probing tip 22. The housing 18 has teeth formed in one end defining slots 24 that are positionable between the leads of an integrated circuit device. The bore 20 extends into one of these slots 24 with the probing tip 22 exposed therein. The other end of the probing tip 22 extending from the other end of the housing 18 for insertion into the socket type probe tip 12. A standard probing tip 26 has a shaft 28 that has one end tapering to a point 30 for probing IC leads, points on a circuit board and the like. The other end of the shaft is inserted into the socket type probe tip 12. The probing tip 26 may also include a cone shaped protrusion 32 formed on the shaft 28 for abutting against the socket type probe tip 12. Adapter 34 is an assembly having a flexible electrically conductive lead 36 attached to an electrical contact shaft 38 that is inserted into the socket type probe tip 12. Adapter 40 has a square pin socket 42 on one end and a contact shaft 44 on the other for inserting into the probe tip 12. The contact shafts for the above described adapters have a length in the range of 0.250 inches.
The above described probe tip adapters may also be used with differential type probes, such as the P6246 Differential Probe, manufactured and sold by Tektronix, Inc., Beaverton, Oreg., the assignee of the instant invention. When used with a differential probe, the adapters are generally ganged together for ease of use. For example, the two flexible electrically conductive lead adapters are positioned in a trapezoidal shaped housing with the flexible electrically conductive leads extending from one end of the housing and the contact shafts extending from the other end of the housing. The flexible electrically conductive leads have a pitch geometry compatible with the leads of surface mounted integrated circuit devices and the contact shafts have a pitch geometry compatible with the socket type probe tips of the measurement probe. Such a probe tip adapter is described in co-pending patent application Ser. No. 08/1738,861, filed Oct. 26, 1996 and assigned to the assignee of the instant invention. Standard probing tips are ganged together with an insulating material, such as plastic, with the contact shaft end having a pitch geometry compatible with the probing tips and the respective probing tip shafts having bends in them to allow the probing tips to match various pitch geometries of surface mounted integrated circuit devices. The bent shaft probing tips may also be rotatable within the insulating material to allow the pitch geometry of the probing tip to be changed to match the pitch geometry of the integrated circuit device. The differential square pin adapter has a housing having contact shafts extending from one end that are compatible with the pitch geometry of the differential probe tip contacts. Extending from the other end of the housing are wires that are attached to the square pin adapters.
Probe tip capacitance and inductance are major drawback to using socket type probe tip or tips in measurement probes. Tip capacitance and inductance limits the input bandwidth of the probe. With the electronic industry continuing to develop integrated and hybrid circuits operating at higher and higher frequencies, a new type of measurement probe design is required that has substantially reduced probe tip capacitance and inductance. This requires reducing the probe tip length and diameter. Likewise, probe tip adapters are required for these low capacitance probes that have reduced length and diameter.
What is needed is a probe tip adapter that is compatible with a low capacitance measurement probe. The adapter should be adaptable to various types of configurations while minimizing as much as possible additional probe tip capacitance and inductance by reducing the length and diameter of the adapters. The adapter should also be attachable to the low capacitance probe tip of the measurement probe over repeated cycles without losing physical or electrical connectivity.
Accordingly, the present invention is to a probe tip adapter for a measurement probe wherein the probe has at least a first probing tip extending from the measurement probe. The probe tip adapter has at least a first electrically conductive element with a bore at one end and a probing contact formed on the other end. Disposed in the bore of the electrically conductive element is an electrically conductive elastomer having sufficient tensile strength, compression set, hardness, deflection force, elongation and percent recovery for repeatably securing the electrically conductive element to the probing tip of the measurement probe. The probing contact may be configured as a probing tip having a shaft that tapers at one end to a point or as a bore formed in the electrically conductive element that receives a spring contact compatible with 0.025 inch square pins. Different configurations of the probing contact are envisioned with one configuration having the shaft of the probing tip being angled. The electrically conductive element is preferably machined as a single part. Alternatively, the electrically conductive element may be formed of a first electrically conductive member associated with the bore end of the element and a second electrically conductive member associated with the probing contact end of the element with the first and second members being joined together.
The probe tip adapter is usable with both a single ended measurement probe and a differential measurement probe. When used with a differential probe, the angled probe tips of the electrically conductive elements are laterally movable from at least a first position having a first pitch geometry to a second position having a second pitch geometry.